Technical Field
This disclosure relates to medical instruments and more particularly to a shape sensing system with rotational constraints and/or control of optical fibers for medical applications.
Description of the Related Art
An optical shape sensing (OSS) fiber can only produce accurate shape reconstruction until about a 2π twist about its axis is reached in either direction, while losing stability close to 6π of cumulative twist. This is due to reconstruction algorithms which compare the signal in three outer cores to a central (no twist) core, and excessive twist along the longitudinal axis of the fiber limits the ability to differentiate phase differences due to bending versus other factors.
Twist can be introduced by an operator while applying a torque to the instrument or to the handle of the instrument as it is manipulated or, by friction between the fiber and the instrument lumen as the instrument is moved. For clinical use, specifically in vascular procedures, surgeons often torque the instrument through multiple π turns, usually in the same direction. The amount of twist which is imparted onto the fiber by the clinician needs to be minimized, while ensuring that the instrument can still be operated and torqued in the usual manner.